/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using Spring.Objects;

namespace Spring.Context.Support;

/// <summary>
/// Convenient superclass for application objects that want to be aware of
/// the application context, e.g. for custom lookup of collaborating object
/// or for context-specific resource access.
/// </summary>
/// <remarks>
/// <p>
/// It saves the application context reference and provides an
/// initialization callback method. Furthermore, it offers numerous
/// convenience methods for message lookup.
/// </p>
/// <p>
/// There is no requirement to subclass this class: it just makes things
/// a little easier if you need access to the context, e.g. for access to
/// file resources or to the message source. Note that many application
/// objects do not need to be aware of the application context at all,
/// as they can receive collaborating objects via object references.
/// </p>
/// </remarks>
/// <author>Rod Johnson</author>
/// <author>Juergen Hoeller</author>
/// <author>Griffin Caprio (.NET)</author>
public abstract class ApplicationObjectSupport : IApplicationContextAware
{
    private IApplicationContext _applicationContext;
    private MessageSourceAccessor _messageSourceAccessor;

    /// <summary>
    /// Creates a new instance of the
    /// <see cref="Spring.Context.Support.ApplicationObjectSupport"/> class.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an <see langword="abstract"/> class, and as such exposes no
    /// public constructors.
    /// </p>
    /// </remarks>
    protected ApplicationObjectSupport()
    {
    }

    /// <summary>
    /// Creates a new instance of the
    /// <see cref="Spring.Context.Support.ApplicationObjectSupport"/> class.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an <see langword="abstract"/> class, and as such exposes no
    /// public constructors.
    /// </p>
    /// </remarks>
    /// <param name="applicationContext">
    /// The <see cref="Spring.Context.IApplicationContext"/> that this
    /// object runs in.
    /// </param>
    protected ApplicationObjectSupport(
        IApplicationContext applicationContext)
    {
        _applicationContext = applicationContext;
    }

    /// <summary>
    /// The context class that any context passed to the
    /// <see cref="Spring.Context.Support.ApplicationObjectSupport.ApplicationContext"/>
    /// must be an instance of.
    /// </summary>
    /// <value>
    /// The <see cref="Spring.Context.IApplicationContext"/>
    /// <see cref="System.Type"/>.
    /// </value>
    protected virtual Type RequiredType
    {
        get { return typeof(IApplicationContext); }
    }

    /// <summary>
    /// Intializes the wrapped
    /// <see cref="Spring.Context.IApplicationContext"/>.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is a template method that subclasses can override for custom
    /// initialization behavior.
    /// </p>
    /// <p>
    /// Gets called by the
    /// <see cref="Spring.Context.Support.ApplicationObjectSupport.ApplicationContext"/>
    /// instance directly after setting the context instance.
    /// </p>
    /// <note type="caution">
    /// Does not get called on reinitialization of the context.
    /// </note>
    /// </remarks>
    /// <exception cref="ApplicationContextException">
    /// In the case of any initialization errors.
    /// </exception>
    /// <exception cref="ObjectsException">
    /// If thrown by application context methods.
    /// </exception>
    protected virtual void InitApplicationContext()
    {
    }

    /// <summary>
    /// Return a <see cref="Spring.Context.Support.MessageSourceAccessor"/> for the
    /// application context used by this object, for easy message access.
    /// </summary>
    public MessageSourceAccessor MessageSourceAccessor
    {
        get { return _messageSourceAccessor; }
    }

    /// <summary>
    /// Gets or sets the <see cref="Spring.Context.IApplicationContext"/> that this
    /// object runs in.
    /// </summary>
    /// <exception cref="Spring.Context.ApplicationContextException">
    /// When passed an unexpected
    /// <see cref="Spring.Context.IApplicationContext"/> implementation
    /// instance that is not compatible with the <see cref="System.Type"/>
    /// defined by the value of the
    /// <see cref="Spring.Context.Support.ApplicationObjectSupport.RequiredType"/>.
    /// property. Also, thrown when trying to re-initialize with a
    /// different <see cref="Spring.Context.IApplicationContext"/> than was
    /// originally used.
    /// </exception>
    /// <exception cref="Spring.Objects.ObjectsException">
    /// If thrown by any application context methods.
    /// </exception>
    /// <exception cref="Spring.Objects.Factory.ObjectInitializationException"/>
    /// <seealso cref="Spring.Context.IApplicationContextAware.ApplicationContext"/>
    public IApplicationContext ApplicationContext
    {
        get { return _applicationContext; }
        set
        {
            if (_applicationContext == null)
            {
                if (!isValueOfRequiredType(value))
                {
                    throw new ApplicationContextException(
                        "Invalid application context: needs to by of type '" + RequiredType.DeclaringType + "'");
                }

                _applicationContext = value;
                _messageSourceAccessor = new MessageSourceAccessor(value);
                InitApplicationContext();
            }
            else
            {
                if (_applicationContext != value)
                {
                    throw new ApplicationContextException("Cannot reinitialize with different application context");
                }
            }
        }
    }

    private bool isValueOfRequiredType(IApplicationContext value)
    {
        if (value.GetType() == RequiredType)
        {
            return true;
        }

        Type[] implementedTypes = value.GetType().GetInterfaces();
        for (int i = 0; i < implementedTypes.Length; i++)
        {
            if (implementedTypes[i] == RequiredType)
            {
                return true;
            }
        }

        return false;
    }
}
